Compositions for delivering benefit agents are well known. Typical formulations include solutions, emulsions, suspensions and gels. The viscosity may vary based on intended area for application, intended use (leave on or rinse off), or consumer preference. When applied to skin, the benefit agent penetrates the skin to some extent, depending on the agent and the formulation.
There is a need for devices and methods that control skin penetration of benefit agents. U.S. Pat. No. 6,419,913 relates to micellar compositions that enhance skin penetration. However, these compositions can be difficult to manufacture and the cost of the products are relatively high. There is also no means for controlling the degree of skin penetration. Ultrasound devices have been utilized to help analgesic compositions and anti-inflammatory agents penetrate skin to help reduce muscle pain and the like. United States patent application 2009/0318852 teaches an ultrasound device for applying agents to skin, which application is herein incorporated by reference. The transducers of the described devices are not oriented within the housing of such devices so as project the generated ultrasound waves at an angle other than at 90° (perpendicular) relative to the surface where the ultrasound is to be applied (e.g., the surface of the skin of a user).